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Heavy-metal contamination of soil has a detrimental effect on Archaea. This bacteria was thought to exist only in extreme environments, but has been found in marine, freshwater, and terrestrial habitats. 16S rRNA sequence analysis shows it belongs to the Crenarchaeota kingdom.

A study was conducted to evaluate the reproducibility and suitability of of competitive polymerase chain reaction (PCR) in soil ecosystems for characterizing population dynamics of indigenous Pseudomonas populations in soil hot spots. Results indicate that competitive PCR accurately quantifies DNA in soil reproducibly even when differences between DNA content and the number of culturable bacteria is only about one order of magnitude.

Microcosm experiments in the fish-pathogenic bacterium Aeromonas salmonicida that serves as a donor reveal the high frequency transfer of the promiscuous plasmid RAS1 in marine sediments, even without a selective factor. DNA probe hybridization reveals that 86.8% of oxytetracycline-sensitive bacterial isolates and 45.8% of oxytetracycline-resistant isolates transfer plasmids, indicating that oxytetracycline promotes transfer frequency. The transconjugants from a oxytetracycline-containing microcosm exhibit less diversity than those from a microcosm lacking a selective agent.

Three strains of Yersinia ruckeri were studied to determine the effect of salinity on growth and survival. Populations of all strains showed an ability to survive at salinities less than or equal to 20%. At 35% salinity, the survival capacity significantly decreased. Direct viable counts (DVC, viable but nonculturable cells) greater than colony-forming units were not detected. Flow cytometry was determined effective in differentiating viable and nonviable cells, as well as for demonstrating genome replication. Six genomes were detected in starved cells of Y. ruckeri.